The invention relates to fluid flow machines in general, and more particularly to improvements in pneumatic or hydraulic pumps (or compressors) which employ one or more fluid-operated valves. The invention also relates to improvements in fluid-operated valves for use in hydraulic or pneumatic pumps, compressors and like machines.
French Pat. No. 627,573 to Ingersoll-Rand Company discloses a valve which can be used in an air compressor and employs a washer-like valving element normally overlying a seat to seal a series of passages for the flow of air. The flowing air can deform the valving element against the convex surface of a fixedly mounted stop. A very large central portion of the valving element is clamped between the stop and the median portion of the seat by a threaded bolt. Valves employing such valving elements can generate considerable noise and the movement of the marginal portion of the valving element against the convex surface of the stop takes up a relatively long interval of time. Therefore, the volumetric efficiency of such valves is not entirely satisfactory.
French Pat. No. 1,346,409 to Etablissements Blancher discloses a valve which can be utilized in the compressor of a refrigerator and is similar to the valve described in French Pat. No. 627,573. Thus, a washer-like valving element can be deformed by the conveyed fluid so that its marginal portion bears against a convex surface of a stop. The major central portion of the valving element is clamped between the stop and the median portion of the seat for the marginal portion of the valving element. The drawbacks of this valve are the same as those enumerated hereinbefore in connection with the compressor valve of French Pat. No. 627,573.
French patent of addition No. 93,448 to Etablissements A. Guiot discloses a fluid-operated valve with an axially movable washer-like valving element which is biased against its seat by a coil spring. The valving element is designed to undergo deformation at elevated temperatures so that it can be flexed away from the seat; however, the valving element is displaced in its entirety at lower temperature when its material can resist deformation by the conveyed fluid.
British Pat. No. 551,275 to The British Thomson-Houston Company, Limited et al. discloses a valve assembly which can be used for air and gas compressors and comprises a washer-like valving element deformable against the convex underside of a curved plate.
U.S. Pat. No. 2,264,136 to Karlberg discloses a compressor valve wherein the valving element is a thin flat metal disc. The valving element and its seat are replaceable.
Swiss Pat. No. 58,481 to Escher, Wyss & Cie. discloses a cylinder for use in pumps or compressors. A flexible disc-shaped valving element is employed to yield when a piston performs a forward stroke to permit a compressed fluid to escape from the cylinder chamber.
Published German patent application Ser. No. 1,960,337 of Lavon discloses a compressor valve. A relatively narrow marginal portion of a disc-shaped valving element can be flexed by flowing fluid to bear against a substantially frustoconical stop opposite a seat which is engaged by the marginal portion of the valving element when the valve is closed.
A drawback which is shared by all of the aforediscussed fluid flow machines and their fluid-operated valves is that the volumetric efficiency of the machine cannot be varied, especially improved, that the valves generate a substantial amount of noise and that the valving elements and/or other parts undergo extensive wear. Such problems are particularly acute in diaphragm pumps or other piston pumps which are used to convey gaseous or other fluids and are equipped with pairs of fluid-operated valves, one for admission of a fluid medium into the pumping chamber when the diaphragm or another piston is caused to perform a suction stroke and the other to permit discharge of fluid from the chamber when the diaphragm or another piston performs a compression stroke. The valving element of one of the valves moves away from its seat in response to the establishment of a pressure differential at its sides, and the same holds true for the valving element of the other valving element. The valving elements are installed in stressed condition so that they tend to move against their seats and to thus close the respective valves. An important advantage of the just described fluid flow machines with fluid-operated valves is that the valving elements are deformable and/or otherwise movable by the conveyed fluid. Thus, one can dispense with mechanical and/or other means for moving the valving elements between open and sealing positions. As a rule, a mechanism for moving a valving element must be lubricated and the lubricant is likely to come in contact with the conveyed fluid which may be detrimental to the fluid and/or to the lubricant. Moreover, the conveyed fluid is likely to attack the material of component parts of the mechanism which is used to move a valving element between open and sealing positions.
An additional drawback of presently known pumps, compressors and other fluid flow machines which employ fluidoperated valves is that their volumetric efficiency is not entirely satisfactory, especially if the piston (e.g., a diaphragm) is moved at a high frequency. The volumetric efficiency can be improved by satisfying two conflicting or non-compatible requirements, namely by ensuring longer opening times for the fluid-operated valve or valves and by ensure abrupt (short-lasting) movements of valving elements to their sealing positions.